I've recently come across some papers, where authors write things like $(1,2,3)^\mathsf{T}$ to refer to the column vector $$\begin{pmatrix}1\\2\\3\end{pmatrix},$$ and avoid confusion with rows (row vectors). I had always been under the impression that commas "$,$" are to be interpreted as "new lines", and an $n$-tuple is automatically treated as an $n\times 1$ (not $1\times n$ vector). I would personally denote a row vector as $\begin{pmatrix}1&2&3\end{pmatrix}$ rather than $(1,2,3)$. Thus adopting my convention, it is perfectly acceptable to say something like: "if $\mathbf x = (1,2,3)$, then $\mathbf{Ax}=(4,5,6)$", where $\mathbf A$ is some $3\times3$ matrix, with out needing any $^\mathsf{T}$ symbols.
I was then told that $\begin{pmatrix}1&2&3\end{pmatrix}$ can be interpreted as a cycle permutation, but I don't think that there is really room for confusion there. What do you think? What is the "standard" interpretation of $(x,y,z)$?
Defining $K^3$ as the set of tuples $(x,y,z)$ with $x,y,z\in K$ and then later on writing these as columns $\left(\begin{smallmatrix}x\\y\\z\end{smallmatrix}\right)$ is common practice to allow multiplying elements of $K^3$ with $3\times 3$ matrices from the left. However, it doesn't hurt to write $(x,y,z)^t$ explicitly when you want to point out to the reader that this should be a column vector and you only write it as a tuple to save space.
I don't think I've heard about the convention "commas in tuples mean new lines" in that wording, instead I'd say we just use both tuples and columns vectors to denote elements of $K^n$.